The source, described as privy to Iran-North Korea ties, told Kyodo Iranian scientists likely were present when the Asian Communist country went through went its third nuclear test Tuesday.
Kyodo said if the Iranian presence is verified, it could further reinforce international community suspicions that Iran is developing nuclear weapons and lead to reassessments in U.S. President Barack Obama's policies toward Pyongyang and Tehran.
The source told Kyodo Iran had suggested to North Korea in November it might observe the test in exchange for paying Pyongyang tens of millions of dollars in Chinese currency.
The Jerusalem Post, citing experts, reported the North Korean test may have been conducted to help Iran avoid international inspections and that Iranian scientists may have been present at the blast site.
Speaking to the Post, Alon Levkowitz -- coordinator of Bar-Ilan University's Asian Studies Program and a member of the BESA Center for Strategic Studies -- noted North Korea's progress both in nuclear weapons capability and intercontinental ballistic missile research.
"The most disturbing question is whether the Iranians are using North Korea as a backdoor plan for their own nuclear program," he told the Post. "The Iranians didn't carry out a nuclear test in Iran, but they may have done so in North Korea."
He said while there is no official information, "Iran may have bypassed inspections via North Korea" and if true, it would be "a very worrying development."
Levkowitz was quoted as saying several indicators pointed to Iranian scientists being present during the North's previous nuclear tests in 2006 and 2009.
He said it had not yet been determined whether North Korea used plutonium or enriched uranium for the Tuesday test but the use of enriched uranium would suggest increased cooperation with Iran.
"There is regular cooperation, since the 1980s, between North Korea and Iran. North Korea also helped set up a plutonium nuclear facility in Syria, which was bombed by Israel in 2007, according to foreign sources," he said.
Iran has maintained its program is intended to produce electricity.